Donor-acceptor Pair Transitions Research Articles

Origin of discrete donor–acceptor pair transitions in 2D Ruddlesden–Popper perovskites

Two-dimensional (2D) van der Waals nanomaterials have attracted considerable attention for potential use in photonic and light–matter applications at the nanoscale. Thanks to their excitonic properties, 2D perovskites are also promising active materials to be included in devices working at room temperature. In this work, we study the presence of very narrow and spatially localized optical transitions in 2D lead halide perovskites by μ-photoluminescence and time-decay measurements. These discrete optical transitions are characterized by sub-millielectronvolt linewidths (≃120μeV) and long decay times (5–8 ns). X-ray photoemission and density-functional theory calculations have been employed to investigate the chemical origin of electronic states responsible of these transitions. The association of phenethylammonium with methylammonium cations into 2D Ruddlesden–Popper perovskites, (PEA)2(MA)n−1PbnI3n+1, particularly in phases with n≥2, has been identified as a mechanism of donor–acceptor pair (DAP) formation, corresponding to the displacement of lead atoms and their replacement by methylammonium. Ionized DAP recombination is identified as the most likely physical source of the observed discrete optical emission lines. The analysis of the experimental data with a simple model, which evaluates the Coulombic interaction between ionized acceptors and donors, returns a donor in Bohr radius of the order of ≃10 nm. The analysis of the spectral and electronic characteristics of these single donor–acceptor states in 2D perovskites is of particular importance both from the point of view of fundamental research, as well as to be able to link the emission of these states with new optoelectronic applications that require long-range optically controllable interactions.

Carbon-related donor–acceptor pair transition in the infrared in h-BN

Experimental studies of intentionally doped impurities for the understanding of conductivity control in hexagonal boron nitride (h-BN) ultrawide bandgap (UWBG) semiconductor are limited but are highly desired for emerging applications of h-BN. We report synthesis by hydride vapor phase epitaxy and comparison photoluminescence (PL) emission spectroscopy studies of intentionally carbon (C)-doped and undoped h-BN semi-bulk crystals. In addition to the well-known C-related emission lines observed previously, a C-impurity-related transition near 1.31 eV consisting of multiple phonon replicas has been observed in C-doped h-BN at room temperature. Phonon replicas involved in the 1.31 eV emission have been identified using polarization resolve PL spectroscopy as the transverse acoustic (TA)/longitudinal acoustic (LA) and out-of-plane optical phonon (ZO) modes at the middle point, T, between the Γ- and K-points in the first Brillouin zone. Based on the agreement between the spectral peak position of the observed dominant emission line at 1.31 eV and the calculated energy-level separation between CB donor (carbon replacing boron) and Ci acceptor (carbon interstitial), the observed IR emission line can be decisively assigned to the donor–acceptor pair (DAP) transition involving the CB donor and Ci acceptor assisted by the intervalley (Κ → Μ) scattering processes. The results reinforce the perception that C impurities form deep-level centers and provided an improved understanding of C impurities in h-BN.

A Combination of Ion Implantation and High‐Temperature Annealing: Donor–Acceptor Pairs in Carbon‐Implanted AlN

Herein, carbon‐implanted high‐temperature annealed (HTA) AlN layers are analyzed and donor–acceptor pair (DAP) transitions probably between the two most abundant impurities, carbon and oxygen, are identified. Both are regarded as the main, hard‐to‐avoid impurities in crystal growth. Oxygen is believed to lead to absorption in the deep UV below a wavelength of 250 nm. In contrast, carbon is the most likely candidate to be responsible for a distinct absorption band around 265 nm. This interpretation has recently been challenged. In this study, carbon‐implanted and HTA AlN layers with ion fluences above 8.1 × 1015 cm−2 are analyzed using low‐temperature and time‐resolved cathodoluminescence spectroscopy. Due to the high concentration of oxygen inside the AlN, as a result of the HTA process, a DAP transition between a most likely carbon‐related acceptor and ON is observed. The measured temperature‐ and power‐dependent blueshift of the peak emission energy as well as the luminescence transients can be clearly explained by a continuous change from a DAP transition at low temperature to a free electron to acceptor transition with increasing temperature. The findings are supported by a configurational coordinate model that describes the measured behavior qualitatively.

Discrete Donor–Acceptor Pair Transitions in CH3NH3PbI3 Perovskite Single Crystals

Achieving a better understanding of the physics of defects in halide perovskites (HPs) is a key challenge for improving the efficiency of the devices. Herein, a comprehensive study of the defect emission of CH3NH3PbI3 perovskite single crystals is presented. The emission of the pristine surface of cleaved crystals is systematically investigated based on steady‐state and time‐resolved micro‐photoluminescence (micro‐PL) spectroscopy. Donor–acceptor pair (DAP) recombination is observed due to the presence of native shallow defects. The DAP spectra present an important variability depending on the location on the surface of the crystals due to inhomogeneous defect distribution. A strong blueshift of the emission is measured as a function of excitation power and is explained by fluctuating potential caused by compensated defects. With increasing photocarrier density, a transition from a structureless to a structured DAP emission with several longitudinal optical phonon replicas is observed. The DAP transition is characterized by the redshift of the emission with time and a slow, non‐exponential PL decay. Sharp discrete lines with sub‐meV widths, the most recognizable spectral signature of DAP transition, are revealed. Herein, the apparently contradictory previous observations on defect emission of CH3NH3PbI3 are reconciled by the results and new insights are provided into the properties of defects in HPs.

Acceleration of the yellow band luminescence in GaN layers via Si and Ge doping

A huge acceleration of the yellow band defect luminescence (YB) with increasing Si and Ge doping concentration in GaN layers has been observed and studied. The donor doping concentrations in the n-type GaN varied from 5 × 10 16 cm −3 to 1.5 × 10 19 cm −3 for undoped, Si-doped, and Ge-doped samples. Consequently, the fastest component of the photoluminescence (PL) decay time curve accelerated from 0.9 ms to 40.3 ns, and the mean decay time from 20 ms to 260 ns with increasing doping concentration. We have proposed an explanation based on a theoretical model of donor-acceptor pair transition (DAP) and electron-acceptor (e-A 0 ) recombination at higher dopant concentrations, which is supported by several measurement techniques as room-temperature radioluminescence (RL), PL measurements or thermally stimulated luminescence (TSL). Last but not least, we have shown a change in the morphology of samples with the increasing dopant concentration, especially 3D columns formation with the high level of Si-doping and its influence on the light extraction from the GaN layer. The paper shows an uncommon way of dealing with slow unwanted YB, which detriment the GaN luminescence properties. • Si and Ge doping of GaN may cause a huge acceleration of yellow band luminescence. • Steady-state photoluminescence intensity remains almost unchanged. • Donor-acceptor and electron-acceptor pair transitions explain the luminescence processes. • Highly Si-doped GaN growths in 3D columns, whereas Ge-doped remains smooth. • The light extraction is influenced by the morphology change.

Optical properties of mist CVD grown κ-Ga2O3

We report on the growth of crystalline κ-Ga2O3 using mist-chemical vapor deposition (CVD) on (0001) sapphire. The κ-phase was confirmed using high-resolution x-ray diffraction (XRD) θ-2θ scan and pole figure-scan of (122) reflex, respectively, while an on-axis full width at half maximum (FWHM) of 104 arcsec was measured in symmetric rocking curve scan. Further, the heteroepitaxial film was analyzed using a mosaic crystal model employing reciprocal space maps (RSM) and a series of asymmetric rocking curve scans. A bandgap of 5.1 eV and excitonic binding energy of 85 meV were estimated from absorption measurements. Built-in field, depletion width, and doping density level were extracted from parabolic WKB model fit. Cathodoluminescence (CL) spectroscopy revealed a defect peak at 329 nm, which was found to be blue-shift with increasing excitation energy, indicating a possible donor-acceptor pair (DAP) transition. Temperature-dependent Current–voltage (I–V) study was performed to extract Schottky barrier height () and ideality factor (η), which were found to be correlated with temperature. Photodetectors fabricated on the sample exhibited pure solar-blind characteristics.

An effect of metal ions (Cu, Mn) doping on the structural, morphological, optical, photoluminescence, electrical and photocatalytic properties of In2S3 nanoparticles

Pristine and Cu, Mn-doped In2S3 nanoparticles (NPs) were synthesized via a simple, elegant co-precipitation route. The dopant (Cu, Mn metal) influence on the structural, optical, photoluminescence and electrical properties were investigated. The (Cu, Mn) dope In2S3 exhibited polycrystalline XRD phases having particle sizes varying from 36.2 to 49 nm. We noted a substantial decrease in the crystallite size on dopant (Cu, Mn) incorporation in In2S3. From FE-SEM images, nanosheets, nanowires, and needle-like structures were observed. EDS elemental detection confirmed that In, Cu, Mn, and S elements are present in the produced NPs. The increment in bandgap (2.8–3.28 eV) was observed after the Cu, Mn doping in In2S3. Photoluminescence studies demonstrate the photoemission is mainly owing to the donor-acceptor pair transitions. The electrical conductivity decreases significantly with doping, and a maximum electrical conductivity of 1.28 × 10−6 (Ω m)−1 was obtained for pure In2S3 NPs. Mn-doped In2S3 exhibits the highest photocatalytic activity (84%) for Methylene blue.

Charge collection and trapping mechanisms in hexagonal boron nitride epilayers

Understanding charge collection and trapping mechanisms is crucial for using hexagonal boron nitride (h-BN) as active layers for many photonic and electronic devices such as deep UV detectors and emitters, neutron detectors, and single photon emitters. Charge collection and trapping mechanisms in h-BN epilayers have been investigated by probing impurity related optical emissions under an applied electrical field. Our results suggested that the existence of oxygen impurities affects the charge collection efficiency and results in an additional emission peak at 3.75 eV, corresponding to a donor-acceptor pair (DAP) recombination involving ON (oxygen residing on the nitrogen site) donors and the VB-H (boron vacancy bonded with hydrogen complex) deep level acceptors. Experimental results further revealed that the applied electric field induces an anti-correlation between the emission intensity of the DAP transition and the charge collection efficiency from which it was shown that it is possible to find an expression to quantitatively measure the maximum charge collection efficiency in h-BN. The results introduce not only a coherent picture for the relationship between common impurities in h-BN and charge collection and trapping mechanisms but also useful insights into possible approaches to improve the quality, purity, and charge collection of the h-BN epilayers.

Low-temperature luminescence in organic-inorganic lead iodide perovskite single crystals

We present a temperature and laser-power dependent photoluminescence (PL) study of methylammonium lead iodide (CH3NH3PbI3) single crystals in the orthorhombic phase. At temperatures below 140 K, we revealed the multi-component PL emission. In addition to a free exciton with an energy of 1.65 eV, we found emission bands with peaks approximately equal to 1.6 eV, 1.52 eV, and 1.48 eV. Analysis of the thermal evolution of the intensities, peak positions, and linewidths of all the PL bands allowed one to determine their origin. We attributed the PL peak with energy of 1.6 eV to a bound exciton, while the free exciton-bound exciton splitting energy is 50–60 meV. The PL emission with an energy of 1.52 eV can be explained by the donor-acceptor pair (DAP) recombination, where donor and acceptor defects have a depth of about 12 meV and 120 meV, respectively. MA (CH3NH3) interstitials (MA) and lead vacancies (V) are the most suitable for the DAP transition to occur in CH3NH3PbI3 crystals. The 1.48 eV PL emission is consistent with the recombination of self-trapped excitons, and interstitial iodine is likely to be an active trap source. We found the variation of the self-trapped depth from 15 meV (at 80 K) to 53 meV (at 80 K) with increasing the temperature. Although the multi-component PL emission in CH3NH3PbI3 single crystals appears at low temperatures, defects and excitonic traps that cause this emission can affect the photophysics of hybrid perovskites at higher temperatures.

Fabrication and characterization of ZnO:Sb/n-ZnO homojunctions

Antimony-doped ZnO layers have been grown by metalorganic vapour-phase epitaxy on sapphire and ZnO substrates at high-temperature (950 °C) and low-pressure conditions (50 torr). Nitrous oxide and diethyl-zinc have been used as oxygen and zinc precursors, respectively. The incorporation of antimony has been obtained from the decomposition of triethylantimony doping molecules added in the gas phase. High Sb concentrations were measured from 1019 to 1021 at/cm−3 using secondary ion mass spectroscopy and depend on the nature and the orientation on the substrate. Low-temperature photoluminescence spectra of Sb-doped layers exhibit donor–acceptor pair transitions at 3.253 eV. Unlike Raman spectra of nitrogen-doped ZnO layers which show several local vibrational modes related to nitrogen incorporation, these modes were found to be absent in the antimony-doped ZnO layers. Transmission electron microscopy suggests that the incorporation of Sb is partly related to dislocations and other structural defects. All together, the characterizations suggest the formation of acceptor dopant–defect complexes, such as SbZn-2VZn. Finally, ZnO:Sb/n-ZnO homojunction diodes have been successfully elaborated on ZnO substrate. The current–voltage characteristics of the device exhibit a rectifying behaviour with a turn-on voltage of 3 V.

Optical Properties of ZnO Deposited by Atomic Layer Deposition on Sapphire: A Comparison of Thin and Thick Films

Optical properties of thin (≈100 nm) ZnO films in comparison with thick (≈1 μm) layers deposited on sapphire substrates by atomic layer deposition (ALD) at temperatures from 100 to 300 °C are investigated by optical transmittance and luminescence. It is found that growth temperature, the thickness of the layers, and post‐grown annealing influence the measured optical bandgap values and low‐temperature photoluminescence. However, the values of the bandgaps corrected according to the Burstein–Moss effect do not depend on layer thickness, whereas an increase in growth temperature leads to a decrease in the energy gap. On the other hand, post‐growth annealing of the layers results in increasing the value of the energy gap and decreasing Urbach energy. It is observed that thicker and annealed samples show more intensive and narrower PL bands, which are assigned to donor and acceptor bound excitons, free electrons to acceptors, and donor–acceptor pair transitions. Their energy position and relative intensity depend on the growth temperature applied.

Effect of the lattice mismatch on threading dislocations in heteroepitaxial GaN layers revealed by X-ray diffraction

In this study, structural investigations of the mismatched gallium nitride (GaN) layers grown on SiC, Al2O3 and Si substrate, were performed employing x-ray diffraction techniques. The resulted threading dislocation density evolved from the lattice mismatch, as a consequence of the strain relaxation processes, was quantified in two independent ways: firstly, using the mosaic block model, which takes into account peak width and, secondly, using the diffuse scattering model, which consider only the tails of the rocking curves. Both models indicated the close relationship between the amount of dislocations and the lattice mismatch that plays a fundamental role in TDs’ generation. To gain further insights regarding threading dislocations, grazing incidence x-ray diffraction was employed to obtain the absorption profiles of the x-rays. Although these profiles encompass the contributions of both sample absorption and dislocations, we decoupled these two effects in the framework of the dynamical theory of diffraction, showing that the existence of dislocations governs different power law dependencies for the experimental absorption profiles. Moreover, the absorption profiles bring information regarding the uniformity of the dislocations along the z-axis, revealing a uniform distribution along the z-axis for thin layer, while for the thick layer an annihilation of the dislocations was taking place. In addition, photoluminescence peaks found at 3.41 eV, 3.39 eV and 3.35 eV correspond to near band-edge (NBE) and ultraviolet donor-acceptor pair (DAP) transition. Significant changes of their intensity ratio, as well as the additional broadening of E2 (high) Raman peak confirm the presence of TDs in the investigated GaN thin films.

Heteroepitaxial growth of β-Ga2O3 films on SiC via molecular beam epitaxy

β-Ga2O3 is a promising ultrawide bandgap semiconductor for next generation radio frequency electronics. However, its low thermal conductivity and inherent thermal resistance provide additional challenges in managing the thermal response of β-Ga2O3 electronics, limiting its power performance. In this paper, we report the heteroepitaxial growth of β-Ga2O3 films on high thermal conductivity 4H-SiC substrates by molecular beam epitaxy (MBE) at 650 °C. Optimized MBE growth conditions were first determined on sapphire substrates and then used to grow β-Ga2O3 on 4H-SiC. X-ray diffraction measurements showed single phase (2¯01) β-Ga2O3 on (0001) SiC substrates, which was also confirmed by TEM measurements. These thin films are electrically insulating with a (4¯02) peak rocking curve full-width-at-half-maximum of 694 arc sec and root mean square surface roughness of ∼2.5 nm. Broad emission bands observed in the luminescence spectra, acquired in the spectral region between near infrared and deep ultraviolet, have been attributed to donor-acceptor pair transitions possibly related to Ga vacancies and its complex with O vacancies. The thermal conductivity of an 81 nm thick Ga2O3 layer on 4H-SiC was determined to be 3.1 ± 0.5 W/m K, while the measured thermal boundary conductance (TBC) of the Ga2O3/SiC interface is 140 ± 60 MW/m2 K. This high TBC value enables the integration of thin β-Ga2O3 layers with high thermal conductivity substrates to meliorate thermal dissipation and improve device thermal management.

Pressure-Dependent Behavior of Defect-Modulated Band Structure in Boron Arsenide.

The recent observation of unusually high thermal conductivity exceeding 1000 W m-1 K-1 in single-crystal boron arsenide (BAs) has led to interest in the potential application of this semiconductor for thermal management. Although both the electron/hole high mobilities have been calculated for BAs, there is a lack of experimental investigation of its electronic properties. Here, a photoluminescence (PL) measurement of single-crystal BAs at different temperatures and pressures is reported. The measurements reveal an indirect bandgap and two donor-acceptor pair (DAP) recombination transitions. Based on first-principles calculations and time-of-flight secondary-ion mass spectrometry results, the two DAP transitions are confirmed to originate from Si and C impurities occupying shallow energy levels in the bandgap. High-pressure PL spectra show that the donor level with respect to the conduction band minimum shrinks with increasing pressure, which affects the release of free carriers from defect states. These findings suggest the possibility of strain engineering of the transport properties of BAs for application in electronic devices.

Carbon related hillock formation and its impact on the optoelectronic properties of GaN/AlGaN heterostructures grown on Si(111)

The integration of GaN on Si as large scale substrates still faces many hurdles. Besides the large difference in the lattice constant and the high thermal mismatch existing between GaN and Si, spiral hillock growth phenomena are common problems in the development of thick GaN layers. In this work, hexagonal hillocks were observed on GaN/AlGaN high-electron-mobility transistor heterostructures grown on Si(111) by metal-organic chemical vapor deposition. The presence of these morphological and structural defects is attributed to the presence of localized contamination at the AlN/Si interface. These carbon-based defects cause highly defective regions in the AlN seed layer, which propagate through all the AlGaN buffer layers inducing the formation of V-shaped pits at the AlGaN interfaces. In hillock regions of the wafers, Raman spectroscopy indicates disturbed two-dimensional electron gas characteristics resulting from GaN/AlGaN interface roughness and a decreased amount of free carriers in the potential well. Energy-dispersive x-ray spectroscopy reveals Ga accumulation inside the V-pits and in nanopipes below, which is responsible for defective areas and the increased GaN growth rate resulting in hillock formation. Photoluminescence measurements confirm the presence of Ga-rich material reducing the inherent gallium vacancy concentration. Here, the reduced amount of Ga-vacancies acting as a shallow acceptor suppresses the ultraviolet luminescence band from donor–acceptor pair transition.

Morphology Effect of 1D ZnO Nanostructures Designed by Hydrothermal and Thermal Annealing for Fast Ultraviolet Photodetector Applications

ZnO nanorods are grown on a ZnO seed layer using the hydrothermal method and subsequently annealed at temperatures of 400–800 °C. The ZnO nanorods annealed at 400 °C exhibit a morphology similar to that of the unannealed ZnO nanorods. However, the tips of the ZnO nanorods gradually become rounded and their density and diameter increase with an increase in the annealing temperature. The intensity of the near‐band‐edge emission increases gradually with an increase in the annealing temperature from 400 to 600 °C but decreases sharply in the case of nanorods annealed at 800 °C. With respect to the deep‐level emissions, broad yellow, orange, and green emissions are observed. Further, the low‐temperature photoluminescence spectrum measured at 12 K of the ZnO nanorods annealed at 600 °C contains a donor‐bound exciton emission, as well as emissions related to the donor–acceptor pair (DAP) transition and the first‐order and second‐order longitudinal optical phonon replicas of the DAP transition. Finally, with respect to the photoresponse, the dark current and photocurrent of the nanorods decrease and their photosensitivity increases with the increase in the annealing temperature.

Conduction mechanisms in ZnO nanowires based Schottky diode grown under an electric field

We present a cathodoluminescence (CL) and electrical study of aligned ZnO nanowires based Schottky diodes synthesized by applying an AC electric field between two Au microcontacts. Our results reveal that the applied electric field aligns the ZnO nanowires between the electrodes and inhibits the formation of ZnO oxygen vacancies (VO). Local CL measurements of ZnO nanowires grown at different zones of the device show that the applied electric field inhibited the formation of oxygen vacancies (VO). Furthermore, CL spectra display an energy shift of the ZnO band edge emission, generated by changes in the relative intensity of two CL bands centered at 3.23 and 3.27 eV that correspond to the donor-acceptor pair and free electrons-acceptor transitions, respectively. We propose the formation of zinc vacancies (VZn) in nanowires that act as acceptor centers in the generation of these two electronic transitions. I-V curves acquired at room temperature reveal the photoresponse of the ZnO nanowires based Schottky diode exposed under UV (365 nm) illumination, exhibiting photocurrent intensities several times higher than that observed under dark conditions for applied bias lower than 1 V. The electrical conduction mechanisms in aligned ZnO nanowires of the device were tunneling and thermionic-emission for applied bias lower than 400 and 700 mV under dark and UV (365 nm) illumination conditions, respectively. For higher bias values, the device showed a conduction mechanism type field-emission.

Planck's generalised radiation law and its implications for cathodoluminescence spectra

Cathodoluminescence (CL) is an important analytical technique for probing the optical properties of materials at high spatial resolution. Interpretation of CL spectra is however complicated by the fact that the spectrum depends on the carrier injection density of the incident electron beam. Here a generalised version of Planck's radiation law is used to uncover the evolution of CL spectra with injection under steady-state conditions. The importance of the quasi-Fermi level is highlighted and it is shown that steady-state luminescence is suppressed when the carrier distributions undergo a population inversion. The theory is consistent with some well-known luminescence phenomena, such as the blue shifting of donor-acceptor pair transitions with increased injection, and its predictions are experimentally verified on CdTe and GaN, which are exemplar thin-film solar cell and light emitting diode materials respectively. Furthermore, the discussion is broadened to include pulsed illumination in time resolved CL, where the carrier distribution is dynamically evolving with time.

Influence of negative-U centers related carrier dynamics on donor-acceptor-pair emission in fluorescent SiC

E 1/E2 defects are the typical negative-U centers in n-type 6H silicon carbide (SiC). They are the main contributors to non-radiative recombination, which limits the carrier lifetime. In this study, two fluorescent 6H silicon carbide (f-SiC) samples and one bulk substrate were characterized via time-resolved photoluminescence (TRPL) and static photoluminescence (PL) measurements, where all the samples were nitrogen-boron co-doped 6H n-type. The existence of E1/E2 defects, which caused the diminution of the internal quantum efficiency (IQE) and luminescence intensity of each sample, was confirmed by applying a carrier dynamics model based on negative-U centers. The carrier dynamics simulation reveals that the density of the E1/E2 defects in bulk 6H SiC is two orders of magnitude higher than that of the f-SiC sample, causing much lower PL intensity in the bulk substrate compared to the two f-SiC samples. The IQE of the two f-SiC samples was extracted from the corresponding TRPL results, where the contrast between their IQE was further confirmed by the related PL measurement results. The slight difference in IQE between the two f-SiC samples was attributed to slightly different E1/E2 defect concentrations. On the other hand, by implementing a steady-state donor-acceptor-pair (DAP) recombination calculation, it was found that the f-SiC sample with lower IQE had a higher DAP transition probability due to the higher doping level. This prompted further optimizations in the f-SiC crystal growth conditions in order to decrease the E1/E2 defects while maintaining the correct doping parameters.

Luminescence properties of heavily doped AlxGa1-xN/AlN films grown on sapphire substrate

Luminescent properties of the AlxGa1-xN films with Si dopant concentration more than 1020 cm−3 grown by molecular beam epitaxy on sapphire substrates with AlN buffer film were investigate at room temperature. Time-resolved photoluminescence spectroscopy was employed to study the donor-acceptor pair transitions in the AlxGa1-xN/AlN/Al2O3 structures with Al mole fraction x from 0.47 to 1 under action of Nd:YAG (λ = 266 nm) laser radiation. The radiation inside planar waveguide consists of spontaneous emission and amplified spontaneous emission. The spontaneous emission spectra demonstrated inhomogeneous broadening with FWHM of 0.58 eV covers full visible range and propagate randomly in all directions. The amplified spontaneous emission propagate at near the critical angle of incidence along zigzag path under total internal reflection conditions at the interfaces of the waveguide. Its spectrum consists of several TEm and TMm modes, which have mutually orthogonal polarizations. The optical measured gains are equals to g ≈ 58 cm−1 for Al0.65Ga0.35N at 510 nm and g ≈ 20 cm−1 for Al0.74Ga0.26N films at λ = 528 nm. The measured values of quantum yields of spontaneous emission for AlxGa1-xN films grow monotonically from 0.11 to 0.79 with increasing x from 0.47 to 0.74. Estimated emission cross-sections for the donor-acceptor pair transitions are more than 10−18 cm2.